1. Field of the Invention
The present invention relates to an audio CODEC (audio coder/decoder) selection controlling system in an integrated network composed of a broad band network (B-ISDN) and a narrow band network (CAS/N-ISDN).
2. Description of the Related Art
In recent years, as technologies of asynchronous transfer mode (ATM) have advanced and become common, the conventional time division multiplexing (TDM) line relaying network has been substituted with ATM line relaying network. To effectively use the band of a communication line, it is necessary to allow an audio CODEC used in a broad band network and an audio CODEC used in a narrow band network to co-exist. Thus, a means for selecting a proper audio CODEC for each audio communication is required.
In a conventional TDM unit, to effectively use the band of a communication line, a reserved dedicated audio CODEC is connected and an audio communication is performed with a reserved compression ratio.
In reality, in an integrated network shown in FIG. 1, audio data of 64 kbps (kilo-bits/second) transmitted from a PBX1a is compressed to audio data of 8 kbps by an audio CODEC (C1) of a TDM unit connected to the PBX1a. The compressed audio data is decompressed to audio data of 64 kbps by the audio CODEC (C1) of a TDM unit connected to a PBX2 on the upper left of the figure.
In addition, audio data of 64 kbps transmitted from the PBX2 is compressed to audio data of 8 kbps by an audio CODEC (C1) of a TDM unit connected on the right of the PBX2. The compressed audio data is decompressed to audio data of 64 kbps by an audio CODEC (C1) of a TDM unit connected to a PBX3a.
At this point, when audio data is relay-connected, if it is repeatedly compressed and decompressed, the quality of audio data deteriorates. Thus, in the case that the type (compression format) of a transmitting side audio CODEC is the same as the type of a receiving side audio CODEC, when a communication route is set between TDM units connected to the PBX2, a communication negotiation is performed therebetween. In this region, audio data is neither compressed, nor decompressed. This system is referred to as digital one-link system. In this system, audio data that has been compressed to 8 kbps by an audio CODEC (C1) of a TDM unit on the PBX1a side is transmitted to a TDM unit on the PBX3a side in the same compression format. The compressed audio data is decompressed by an audio CODEC (C1) of the TDM unit.
However, in the related art reference, each TDM unit does not have a route selecting function. Instead, the PBX2 selects a route. Thus, in FIG. 1, when the PBX1a and the PBX3b are connected, since the type of the audio CODEC (C1) of the TDM unit connected to the PBX1a is different from the type of the audio CODEC (C2) of the TDM unit connected to the PBX3b, the digital one-link cannot be accomplished with the PBX2 interposed therebetween.
The present invention is made from the above-described point of view. An object of the present invention is to provide a function for allowing an AWN broad bandxe2x80x94narrow band connection node unit to select an audio CODEC corresponding to a route of a connected destination side narrow band network considering that an ATM-WAN node has a function for deciding a route corresponding to address information of a narrow band network so as to accomplish a digital one-link system in an integrated network.
The present invention is based on a broad bandxe2x80x94narrow band connection node unit (AWN 5) for communicating digital data between a narrow band network and a broad band network in an encoding/decoding format that is the same as an encoding/decoding format used on a communication route in the narrow band network of an integrated network composed of the broad band network and the narrow band network.
At least one encoding/decoding unit (an audio CODEC 9 or a video encoding/decoding unit 203) has a digital one-link function that causes compressed digital data (audio data and/or video data) to be passed and compressed/decompressed only at a communication termination point depending on the setting of the compressed digital data so as to prevent the quality of the digital data from deteriorating.
An individual route encoding/decoding type managing unit (narrow band destination route audio CODEC management table b) stores the relation between each destination route (PBX node number) in the narrow band network and each type of the encoding/decoding unit used on each route.
An encoding/decoding unit selecting unit (a narrow band call controlling unit 12, a narrow band signaling controlling unit 13, a TDM-SW controlling unit 14, or a narrow band route decision controlling unit 15) asks the individual destination route encoding/decoding type managing unit for the type of the encoding/decoding unit corresponding to the destination route information (PBX node number) included in signaling data and selecting one of the encoding/decoding unit, among a plurality of encoding/decoding units, corresponding to the obtained type.
In the structure of the present invention, after the broad bandxe2x80x94narrow band connection node unit that is directly connected to a route selecting unit (a PBX2) in the narrow band network selects an encoding/decoding unit corresponding to a destination route in the narrow band network, the broad bandxe2x80x94narrow band connection node unit informs a destination side broad bandxe2x80x94narrow band connection node unit of the type information of the selected one of the encoding/decoding units and the destination side broad bandxe2x80x94narrow band connection node unit selects one of the encoding/decoding units corresponding to the informed type information.
In such an additional structure, the broad bandxe2x80x94narrow band connection node unit that is directly connected to the route selecting unit in the narrow band network selects one of the encoding/decoding units corresponding to the type information of the encoding/decoding unit that is used in the destination route and received from the route selecting unit.
Moreover, in the structure of the present invention, when the type of the encoding/decoding unit used in the narrow band network is changed during communication, the broad bandxe2x80x94narrow band connection node unit and the destination side broad bandxe2x80x94narrow band connection node unit exchange the type information of the encoding/decoding unit that was changed so as to change the encoding/decoding unit used in the broad bandxe2x80x94narrow band connection node unit and the destination side broad bandxe2x80x94narrow band connection node unit to the encoding/decoding unit corresponding to the type information.
According to the present invention, since each encoding/decoding unit used in a broad band network is matched with each encoding/decoding unit used in a narrow band network, the conventional encoding/decoding unit can be connected in data one-link structure. Thus, in addition to the multiplexing function of a broad band network, communication data can be compressed. Consequently, the transmission efficiency can be further improved.